Field of Invention
The present invention relates to a field of biologic electrical impedance detecting technology, and more particularly to an electrical impedance detecting device of a portable electrical impedance imaging system and a detecting method thereof.
Description of Related Arts
Biologic electrical impedance imaging technology is a tomography technology for displaying the inner structures of organisms by utilizing the information of electrical impedance detected on the body surface without wound. The technology may use an electrical impedance detecting device for detecting electrical impedance of the imaging target to obtain a set of electrical impedance value illustrating the inner information of the imaging target at a certain frequency. A constant excitation current should be applied on the imaging target for detecting the response voltage when detecting electrical impedance, the information of electrical impedance can be obtained by demodulating the response voltage signals.
In a conventional electrical impedance imaging technology, when detecting electrical impedance, excitation sinusoidal current signals are sent to the imaging target, and the response sinusoidal voltage signals are rapidly sampled by high-speed analog-to-digital converter (ADC). Then the information of electrical impedance is obtained by utilizing digital quadrature demodulation for demodulating the response sinusoidal voltage signals.
In a conventional bioelectrical impedance detecting circuit, chips like FPGA and high-speed ADC are needed, and a large number of multiplication operations should be performed when utilizing digital quadrature demodulation. All these lead to complex calculation in CPU and high power consumption. Thus, the conventional electrical impedance imaging technology is not adaptable to being used in a portable electrical impedance imaging system powered by battery.
Therefore, a method with simple structure, simple calculation and low power consumption for detecting bioelectrical impedance is needed to meet the requirements that a portable electrical impedance imaging system should be small in size and low in power consumption.